http://worldcat.org/entity/work/id/137026991

Impulse response of linear systems using correlation and direct measurement

If a pseudo-random noise sequence is used as the input to a linear system, then by suitably correlating the output of the system and a delayed version of the input, the impulse response of the system can be obtained. The effect of the finite size of the sequence auto-correlation function upon the expected results is analytically determined. A system for making the measurements, including a simple method of obtaining a delayed sequence, is described. Measurements were made on low pass rc filters and comparisons made with the predicted results. A polarity-coincidence correlator was used. It was found that best results were obtained when the correlator output vs normalised correlation coefficient curve was assumed to be linear, although an accurate determination of the correlator characteristic could not be made. Finally, impulse response measurements were made on three speakers using correlation, direct pulsing and differentiation of the step response and the three methods compared. (Author).

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